The present invention relates to electrical connectors that are typically used in high-performance aircraft and other vehicles, that must withstand severe vibration and other adverse environmental conditions.
Connector assemblies for severe environments are typically held in mating engagement by a clamp ring of one connector portion threadingly engaging the mating connector portion. Traditionally, the clamp ring is held in its clamping state by having the ring configured with a single lead thread having a pitch of about 20 threads per inch, and by the use of safety wire. More recently, coarser and/or multiple-lead threads have been preferred for permitting rapid coupling and uncoupling of the assemblies. Connectors of this type include those known as "Series III" connectors that are specified in standard shell sizes 9-25 for many high-performance applications according to MIL-C-38999/26D (dated May 7, 1990), which is incorporated herein by this reference.
When Series III connectors are subjected to heavy vibration, it is required that the mating portions maintain a solid metal-to-metal face contact. It is also required that the performance under vibration be maintained even after a certain minimum number of complete engagements and disengagements of the mating portions. For this purpose, some form of locking device is provided for the clamp ring. With reference to FIGS. 1-3, one form of locking device presently in use includes a set of ratchet teeth 10 that project outwardly from a first shell member 11, one or more detent members 12 being carried on respective spring members 13 by a threaded clamp ring 14 that is rotatably connected to the first shell member 11. Rotation of the ring 14 in a clamping direction (as indicated by the arrow in FIG. 1) for clamping to a second shell member (not shown) is accompanied by ratcheting of the detent members 12 over the teeth 10, the teeth 10 each having a moderately inclined first ramp surface 15 that resists the clamping direction of rotation. Also, each of the teeth 10 has a more steeply inclined second ramp surface 16 that heavily resists rotation of the ring in an opposite, unclamping direction.
The prior art connectors of the type shown in FIG. 1 are subject to one or more of the following disadvantages:
1. The locking device is ineffective in that it does not maintain the required solid metal-to-metal face contact in that the discrete detent positions do not necessarily lie in phase with the fully clamped position of the ring such that even a slight vibration can cause the ring to back off slightly, the face-to-face contact being immediately lost when pressure is released from a compressively loaded elastomer that typically seals contact pins of the connector;
2. The locking device is ineffective in that the detent members do not prevent continued rotation in the unclamping direction, particularly after a number of engagement cycles, because the detent members have very little contact surface area, rapidly wearing away the teeth; and
3. The locking device is unreliable in that harmful foreign matter is not excluded, being damaged when the connector is decoupled, such as when water freezes within the device.
As shown in FIG. 2, a variation of the locking device of FIG. 1 has the detent members 12 formed in pairs that are slightly out of phase for providing detent positions in a multiple of the number of teeth. Each pair of the detent members 12 is located on a multiply supported counterpart of the spring member, designated 13', the spring member 13' rocking slightly on a middle support as indicated at 17 in FIG. 2, one of the detent members 12 moving inwardly as the other moves outwardly between detent positions. The prior art configuration of FIG. 2 suffers from each of the above disadvantages except to the extent that the greater number of detent positions limits the backing off of the clamp ring 14 to the first detent engagement. A further disadvantage of the configuration of FIG. 2 is that it is more expensive and complicated to assemble in that a multiple complement of the detent members 12 is required for obtaining the same locking torque.
As shown in FIG. 3, another variation of the locking device of FIG. 1 has the teeth, designated 10', projecting axially from a counterpart of the first shell member, designated 11'. Several of the detent members (typically four or six), designated 12', are formed on an annular detent plate 18 that has outwardly projecting tabs 18' for keyed engagement with a counterpart of the clamp ring, designated ring 14'. The detent members 12' are axially biased against the teeth 10' by a wavy spring washer, designed spring member 13". The spring member 13" is supported within the clamp ring 14' by a first retaining clip 19. A second retaining clip 19' clamps against the first shell member 11' opposite the teeth 10' when the ring 14' is advanced in the clamping direction of rotation.
The prior art configuration of FIG. 3, while failing to overcome the disadvantages of the previously described prior art configurations, has other serious problems. For example, the clamp ring 14' must overcome the axial force from spring member 13" in addition to the other sources of resistance to clamping of the mating connector portions. Conversely, the spring member 13" continuously urges the mating portions apart, hastening failure of the connector. Also, the retaining clips 19 are considered to be unreliable, failure of the clip 19' catastrophically rendering the clamp ring 14' completely ineffective in holding the connector in its mated condition. Further, the spring member 13" makes only spaced apart contact with the detent plate 18, typically at from three to six locations, subjecting the relatively thin plate 18 to undesirable bending deflections between the spaced apart detent members 12' that produce uncontrolled variations in the biasing forces, and possible failure of the detent plate 18 by fatigue.
Thus there is a need for a connector having a locking device that overcomes the above disadvantages.